Electrodeposition of iron



Patented May 13, I947 sates OFFICE 2,420,403 ELEornoDErosrrroN .oF IRONNo Drawing. Application February 25, 1943,

.Serial No. 477,131

22'Claim's. 1

invention relates to the electrodeposition of iron and is hereindescribed as embodied in a plating bath of improved composition withwhich it is possible to secure deposits which are uniform-1yfine-grained and smooth and possess a combination of strength andductility not heretofore obtained in electrodep-osited iron withoutsubsequent heat treatment.

Electrodeposition of iron has in the past found relatively littlepractical use, due in part to the hardness and brittleness of thedeposits commonly secured by this method, and in part to the difiicultyof controlling the deposition to maintain the desired uniformity andconsistency in the results secured.

Iron deposits have been made from solutions of ferrous salts, usuallythe chloride or sulfate. Deposits from the chloride have been made withfine-grained structure of good strength at the beginning of thedeposition but it was found that as deposition continued the graincoarsened so that the deposit had good strength only on the surfacefirst deposited. Deposits so made could be bent in one direction butwould fracture readily if bent in the other direction. Suchcharacteristics naturally seriously limited the use of iron deposited asdescribed.

Furthermore, it has in the past been necessary, in order to secure aniron deposit having a reasonable degree of ductility, to carry out thedeposition at temperatures from about 190 to 220 or more degreesFahrenheit, which was in many cases found to be disadvantageous. It hasalso been necessar heretofore to very closely control the temperatureand hydrogen ion concentration in the baths from which iron wasdeposited, since When a relatively small change was made in either ofthese conditions, great differences were found in the structureand-physical properties .of the resulting iron deposit.

I have now discovered that the addition of a small amount of solublemanganese to the plating bath serves to prevent a coarsening of thegrain as the deposition continues, and makes possible the deposition ofiron in a uniformly fine-grained and ductile form of good strength, attemperatures materially lower than hereto fore required. I have alsodiscovered that the addition of manganese to the bath appears tomaterially broaden the permissible operating range of temperature andhydrogen ion concentration within which it is possible to securedeposits of good strength and ductility. For instance, by'the additionof manganous chloride in amounts equivalent to 1.4 grams of solublemanganese per liter to a bath containing, say 300 grams of ferrouschloride (-FeClz-lI-IaO), which is equivalent to about '84 grams ofsoluble iron, per liter, I have been able to secure an iron depositwhich is truly ductile, strong, and of uniformly fine rain structure,when the bath was maintained at a temperature between 160 and 220 and a.pH value between 1.2 and 2.6. In a ferrous sulfate bath the manganeseserves to ref ne the rain structure but has not served to produce adeposit which is truly ductile without heat treatment, apparentlybecause of the tendency of sulfate solutions ,to cause hydrogenemhrittlement. V

Manganese in the bath appears to be effective to refine the grainstructure of 'electrodeposited iron when present in amounts as small asit gram of soluble manganese per liter. The effect seems to increasewith increasing amounts of manganese up to about 1.4 grams per liter.Little if any advantage, however, appears to be secured by furtherincreases in the amount, though amounts up to 17 or 20 or more grams perliter have been used successfully.

The manganese is advantageously added to the ferrous chloride andferrous sulfate solutions in theform of manganous chlorideand manganoussulfate respectively. :It may, however, he added in any one of a varietyof other forms, such as other salts of manganese or even salts ofmanganic or permanganic acid, which in the ferrous chloride or sulfatesolutions react to liberate ions of divalent manganese. The use of saltssuch as the nitrate, formate, etc., carrying acid radicals which enterinto the cathode reaction, should be avoided.

It may also be noted that the action of the manganese is apparentlycatalytic in nature, no evidence having been discovered to indicate thatany of the manganese in the bath is consumed during theelectrodeposition of the iron, or that even small amounts of manganesehave been deposited with the iron.

When using the chloride solutions of the present invention, I find itadvantageous to maintain therein a pH value between 1.2 and 2.6, andpreferably between 1.8 and 2.3 as measured at room temperature by glasselectrode equipment,

thegreatest ductility having been secured with 3 using a chloridesolution modified according to the present invention, the requiredacidity is advantageously secured by addition of hydrochloric acid.

4 As in the case of the usual baths, the current densities which may beused are higher at higher temperatures and lower at lower temperatures.For example, at temperatures above 200 F. I have When using a sulfatebath containing man- 5 been able to use current densities as high as 300ganese in accordance with the present invention, amperes per squarefoot; at temperatures of 170 the pH of the solution is advantageouslymain- F. 100 amperes per square foot; and at 160 F. 50 tained at a valuematerially higher than in the amperes per square foot. case of achloridebath, since at values as low The presence in the solution of aslittle as 5 as 2 the anodes are attacked with great vigor milligrams oflead per liter noticeably interferes and much gas is liberated at thecathode, indiwith the deposition of iron, and 250 milligrams eatingreduced efficiency. The addition of manper liter completely prevents theformation of ganese to the solution, as described, advanany usefuldeposit. Consequently the bath used tageously in the form of manganoussulfate, should be substantially free from lead, and the serves toimpart a refined grain structure to iron use of lead-lined tanks orother lead equipment deposits made from solutionshaving pH values shouldbe avoided. Other precautions, well unfrom 2 up to 4.5 or more. derstoodby those skilled in the art, should be As in the prior art, so also inthe deposition taken to insure the purity of the bath, such as of ironfrom the solutions of the present inventhe use of pure chemicals andanodes, specifically tion, the higher the temperature of the bath thesuch as are substantially free from such impurigreater the ductility ofthe deposit. By the use ties as arsenic, copper, tin, lead, etc. Theanodes of my improved solution, however, I find it posshould beenclosed, as by any of the known desible to secure fine-grained ductiledeposits of vices, e. g. porous cups, glass or asbestos bags, iron attemperatures from 30 to 50 F. lower etc. to maintain the cleanliness ofthe solution than those heretofore required. and prevent the resultingroughening of the de- I have frequently observed a tendency towardposit. In case of the contamination of the bath pitting of the deposit,which appears to be more by organic materials, treatment with an inertserious at lower temperatures; but I have found, adsorbent material suchas activated carbon, is however, that this tendency toward pitting cansometimes advantageous. To avoid trouble be prevented and the characterand smoothness caused by oxidation of the solution by contact of thedeposit greatly improved by the addition with the air, it may be coveredwith a layer of to the solution of a small amount of a sodium mineraloil, molten paraffin, or the like, to presalt of a sulfated higher fattyalcohol. For exvent such contact, Further, it is frequently adample, theproducts known to the trade as vantageous to subject the baths of thepresent Gardinol and Tergitol have been found efinvention to thebreaking-in period, well fective in amounts approximating one gram perknown in the art, wherein the solution is subliter, though there appearsto be nothing critical jected to electrolysis for a short time before itabout the proportion used, and a considerable is placed in service.variation can apparently be made in the per- The following table givesthe pertinent facts centages used while still securing the advantagesregarding a number of examples which illustrate described. With thesolution so modified I have the use of various solutions embodying thepresfound it possible to operate successfully securent invention in theformation of electrolytic ing fine-grained deposits of good strength andiron deposits having improved rai St ucture ductility at temperatures aslow as 160 F. and ductility.

No. chloride sulfate chloride Sulfate WA 1.017 a F: l000#/1n.'- per centsands 1 84 1.4 20s 100 51 44 2,244 f gg gf f fgfgffg ductility for iron.

2 84 1.4 194 2.1 100 Fine-grained ductile deposit. Badly pitted.

3 S4 1.4 $4 104 2.1 100 Fine-grained ductile deposit. Freeirom pitting.

4 cs 0.8 1 170 23 1, 900 deposit free from pitting.

5 cs 0.8 1 50 111 12.5 1, 390 igggit ttts'iitii from pitting.

6 60 1.2 3.0 100 Smooth finegrained deposit only slightly ductile.

7 s4 1.4 205 100 47.5 50 2, s75 g g gggf fiflg i tionally ductile.

The concentration of ferrous iron in the solutions may be varied overrather wide limits.

In the foregoing table the product of percent elongation and tensilestrength is included to fur- Solutions containing less than 45 and morethan 70 nish a basis of comparison of the strength-duc- 200 grams ofiron per liter in the form of ferrous chloride have been usedsuccessfully. With the higher concentrations it is in general possibleto operate at somewhat lower temperatures than with the lowerconcentrations.

tility properties of the deposits with the same properties of knownforms of iron. This product. in the case of commercial soft irons andlow carbon steels where ductility is a requirement, has a commonlyaccepted value of about 1,500,000.

For example, a representative cold rolled strip steel in a soft temper,intended for forming and drawing operations Where ductility is ofprimary importance, may have a tensile strength of about 50,000 poundsper square inch and an elongation of about 30 per cent. Use of thesolutions of the present invention is'thus seen to'make possible theproduction by electrolytic deposition, of iron which amply fulfills thepresent day strength-ductility standards set for commercial ductileiron. Even where the deposition was car ried out under conditions toyield a deposit of tensile strength which is exceptionally high forsubstantially pure iron, it will be noted thata good degree of ductilitywas nevertheless secured.

Not only do the solutions of the present inven tion make possible theproduction of uniformly smooth and fine=grained deposits, but they arealso found to be materially less sensitive to Vari atiohs in temperatureand in hydrogen ion concentration than were those of the prior art.Therefore, with my solutions it is not necessary to maintain theextremely accurate control of temperature and pd formerly required inorder to produce iron deposits of satisfactory uniformity. With thesesolutions, also, it is possible to substantially if not entirelyeliminate the evolution of gas and to secure cathode efiiciencies of 96to 98 percent or better. Operating temperatures may be from 30 to 50degrees F. lower than heretofore while securing an iron deposit whichpossesses equal or superior ductility and fineness of grain structure.

The use of my solutions is thus seen to make possible a novelcombination of broad operating range of temperature and pl-l with finegrain, good strength, and ductility of the resulting iron deposit.

I claim:

1. The process of obtaining smooth, finegrained deposits of iron from anelectrolytic bath consisting essentially of an aqueous solution of asalt from the class consisting of ferrous chloride and ferrous sulfatewhich comprises passing an electric current through the bath whilemaintaining therein, as a catalytic refining agent, at least one-tenthgram and not substantially more than twenty grams per liter of solublemanganese in the form of a divalent salt from the class consisting ofmanganous chloride and manganous sulfate, the pH of the bath beingbetween 1 and 4.5 but not sufilciently high to cause a coarse grainstructure of the deposited iron.

2. The process of obtaining smooth, finegrained deposits of iron from anelectrolytic bath consisting essentially of an aqueous solution offerrous chloride which comprises passing an electric current through thebath while maintaining therein, as a catalytic refining agent, at leastone-tenth and not substantially more than twenty grams per liter ofsoluble manganese in the form of a divalent salt from the classconsisting of mange-nous chloride and manganous sulfate, the pH of thebath being between 1 and 3.

3. The process of obtaining smooth, finegrain'ed deposits of iron froman electrolytic bath consisting essentially of an aqueous solution offerrous chloride which comprises passing an electric current through thebath while maintaining therein, as a catalytic refining agent, at leastonetenth and not substantially more than twenty grams per liter ofsoluble manganese in the form of a divalent salt from the classconsisting of m'anganous chloride and a manganous sulfate, the pH of thebath being between 1.2 and-2. 6;

4. The process of obtaining smooth} sne grained deposits of iron fromanelectrolytic bat-h consisting essentially of an aqueous senses offerrous chloride which comprises pa ssinga-n sledtric current throughthe bath While maintaining therein, as a catalytic refining gent; atleast one-tenth and'not substantially more than twenty grams per literof soluble manganese in the formof a divalent salt from the classconsisting of manganous chloride and manganous's ulfate; the pH of thebath being between 1.8 and 2.3;

5. The process of obtaining smooth,- finegrained deposits of iron froman electrolytic bath consisting essentially of anaqueous solutionofferrous sulfate which comprises passing an electric current through thebath while maintaining therein, as a catalytic refining agent, atleastone-tenth gram and not substantially moretha'n twenty grams per liter ofsoluble manganesein the form of a divalent salt from the class consisting of manganous chloride and manganous sulfate, the pH of the bathbeing between 2 and 4.5.

6. The process of. obtaining smooth; finegrained deposits of iron froman electrolytic bath consisting essentially of an aqueous solution offerrous sulfate which comprises passing an electric current through thebath While maintaining therein, as a catalytic refining agent, at leastone-tenth gram and not substantially more than twenty grams per liter ofsoluble manganese in the form of a divalent salt from the classconsisting of man anous chloride and manganous sulfate, the pH of thebath being about 3.

'7. The process of obtaining smooth, finegrained deposits of iron froman electrolytic bath consisting essentially of an aqueous solution of asalt from the class consisting of ferrous chlo: ride and ferroussulfate, and a sodium salt of a sulfated higher fatty alcohol, whichcomprises passing an electric current through the bath while maintainingtherein, as a catalytic refining agent, at least one-tenth gram and notsubstantially more than twenty grams per liter of soluble manganese inthe form of a divalent salt from the class consisting of manganouschloride and manganous sulfate, the pH of the bath being between 1 and4.5 but not suificiently high to cause a course grain structure of thedeposited iron.

8. The process of obtaining smooth, finegrained de'posits'of iron froman electrolytic bath consisting essentially of an aqueous solutionofferrous chloride and a sodium salt of a'sulfated higher fatty alcohol,which comprises passing an electric current through the bath whilemaintaining therein, as a catalytic refining agent, at least one-tenthgram and not substantially more than twenty grams per liter of solublemanganese in the form of a divalent salt from the class consisting ofmanganous chloride and manganous sulfate, the pH of the bath beingbetween 1.2 and 2.6.

9. The process of obtaining smooth, finegrained'deposi'ts of iron froman electrolytic bath consisting essentially of an aqueous solution of asalt from the class consisting of ferrous chloride and ferrous sulfatewhich comprises passing an electric current tlirough'the bath whilemaintaining therein, as a catalytic refining agent, at least one-tenthgram and not substantiallymore than twenty grams per liter of solublemanganese in the form of a divalent salt from the class consisting ofman'gan'ous chloride and nianganous sulfate, the pH of thebath beingbetween 1' and 4.5 but not .sumciently high to cause" a course grainstructure of the deposited iron, maintaining the current density betweentwenty-five and three hundred amperes per square foot at the cathodesurface, and maintaining the bath during the electrodeposition of theiron at a temperature between 160 F. and 220 F.

10. The process of obtaining smooth, finegrained deposits of iron froman electrolytic bath of an aqueous solution consisting essentially offerrous chloride which comprises passing an electric current through thebath while maintaining therein, as a catalytic refining agent, at leastone-tenth and not substantially more than twenty grams per liter ofsoluble manganese in the form of a divalent salt from the classconsisting of manganous chloride and manganous sulfate, the pH of thebath being between 1.2 and 2.6, maintaining the current densitybetweentwenty-five and three hundred amperes per square foot at thecathode surface, and maintaining the bath during the electrodepositionof the iron at a temperature between 160 F. and 220 F.

11. The process of obtaining smooth, finegrained deposits of iron froman electrolytic bath consisting essentially of an aqueous solution offerrous chloride which comprises passing an electric current through thebath while maintaining therein, as a catalytic refining agent, at leastone-tenth and not substantially more than twenty grams per liter ofsoluble manganese in the form of manganous chloride, the pH of the bathbeing between 1 and 3.

12. The process of obtaining smooth, finegrained deposits of iron froman electrolytic bath comprising essentially a solution in water of thecations of divalent manganese and divalent iron, and anions from theclass consisting of chloride and sulfate which comprises passing anelectric current through the bath while maintaining the divalentmanganese cations therein to the extent of at least one-tenth gram perliter and sufficient to cause grain refinement of the deposited iron,but not to an extent suflicient to cause deposition of manganese alongwith the deposition of iron under the deposition conditions recited, andmaintaining the pH of the bath during deposition between 1 and 1.5 butnot suificiently high to cause a coarse grain structure of the depositediron, the divalent manganese cations acting as a refining agent.

13. A plating bath for the electrodeposition of iron comprisingessentially a solution in water of the cations of divalent manganese anddivalent iron, and anions from the class consisting of chloride andsulfate, the divalent manganese cations acting as a catalytic refiningagent and being present in an amount not less than about one-tenth gramper liter and in an amount sufficient to cause grain refinement but notin an amount sufiicient to cause deposition of manganese along with thedeposition of iron when an electric current is passed through the bathto cause electrodeposition of iron therefrom, the pH of the solutionbeing between 1 and 4.5, but not sufiiciently high to cause a coarsegrain structure of the deposited iron.

14. A plating bath for the electrodeposition of iron comprisingessentially a solution in water of the cations of divalent manganese anddivalent iron, and anions from the class consisting of chloride andsulfate, the divalent manganese cations acting as a catalytic refiningagent and being present in an amount between about onetenth gram andtwenty grams per liter, said bath having a pH between 1 and 4.5, but notsufficiently high to cause a coarse grain structure of the depositediron.

15. A plating bath for the electrodeposition of iron comprisingessentially a solution in water of the cations of divalent manganese anddivalent iron, and chloride anions, the divalent manganese cationsacting as a cataytic refining agent and being present in an amountbetween about one-tenth gram and twenty grams per liter, the pH of thesolution being between about 1 and 3.

16. A plating bath for the electrodeposition of iron comprisingessentially a solution in water of the cations of divalent manganese anddivalent iron, and chloride anions, the divalent manganese cationsacting as a catalytic refining agent and being present in an amountbetween about onetenth gram and twenty grams per liter, the pH of thesolution being between 1.2 and 2.6.

17. A plating bath for the electrodeposition of iron comprisingessentially a solution in water of the cations of divalent manganese anddivalent iron, and chloride anions, the divalent manganese cationsacting as a catalytic refining agent and being present in an amountbetween about onetenth gram and twenty grams per liter, the pH of thesolution being between 1.8 and 2.3.

18. A plating bath for the electrodeposition of iron comprisingessentially a solution in water of the cations of divalent manganese anddivalent iron, and sulfate anions, the divalent manganese cations actingas a catalytic refining agent and being present in an amount betweenabout onetenth gram and twenty grams per liter, the pH of the solutionbeing between about 2 and 4.5.

19. A plating bath for the electrodeposition of iron comprisingessentially a solution in water of the cations of divalent manganese anddivalent iron, and sulfate anions, the divalent manganese cations actingas a catalytic refining agent and being present in an amount betweenabout onetenth gram and twenty grams per liter, the pH of the solutionbeing about 3.

20. A plating bath for the electrodeposition of iron comprisingessentially a solution in water of a sodium salt of a sulfated higherfatty alcohol, cations of divalent manganese and divalent iron, andanions from the class consisting of chloride and sulfate, the divalentmanganese cations acting as a catalytic refining agent and being presentin an amount not less than about one-tenth gram per liter and sufiicientto cause grain refinement of the deposited iron, but not in an amountsufficient to cause deposition of manganese along with the deposition ofiron when an electric current is passed through the bath to causeelectrodeposition of iron therefrom, the pH of the solution being notsuificiently high to cause a coarse grain structure of the depositediron.

21. A plating bath for the electrodeposition of iron comprisingessentially a solution in water of a sodium salt of a sulfated high'erfatty alcohol, cations of divalent manganese and divalent iron, andchloride anions, the divalent manganese cations acting as a catalyticrefining agent and being present in an amount between about onetenthgram and twenty grams per liter, the pH of the solution being betweenabout 1 and 3.

22. A plating bath for the electrodeposition of iron comprisingessentially a solution in water of ferrous chloride and manganouschloride, the manganous chloride being present as a catalytic refiningagent and in an amount suflicient to provide between about one-tenthgram and 9 l0 twenty grams per liter of manganese, said solu- NumberName Date tion having a pH between about 1 and 3. 2,254,161 Waite et a1Aug. 26, 1941 2,316,917 Wallace Apr. 20, 1943 WILLIAM B. STODDARD, J R.a FOREIGN PATENTS REFERENCES CITED Number Country Date The followingreferences are of record-in the 288660 Germany 1915 file of this patent:OTHER REFERENCES UNITED STATES PATENTS 0 Modern Electroplatlng, specialvo1., Electro- Number Name Date chemical Society 1942, page 273. (Copyin Divi- 1,215,354 Eaton Feb. 13, 1917 1,377,822 Eustis May 10, 1921

